How do you know if you're not in a relationship anymore

So a couple days ago I told my bf I think my feelings for him were fading. I'm 19 and this is my first relationship which means I've been single all my life. I told him it could be that I miss being single but I didn't know...(fast forward)...after the last thing I told him he hasn't responded back or written me. So recently I messaged him said his name he said "what's up". I asked if he was ok and he said "yeah I'm good". He's answering me in short sentences. I don't know what to do :( :( :(